Alerts from police, fire and emergency management agencies will appear on Google maps and search pages beginning Friday as part of a growing Google public alert system.

Google has partnered with Nixle, a company that contracts with public safety agencies to send alerts via cellphones and social media. Police and sheriff's departments in Chicago, Dallas and Los Angeles are among agencies using the service.

The alerts will appear when someone uses Google in an area with an active alert or searches for a place that has an active alert.

There are 6,500 police agencies that use Nixle. Those agencies serve more than 150 million people, but of that potential audience, only 2 million people subscribe to alerts, Nixle CEO Eric Liu says.

"It's not on a person's mind until you're in a crisis situation," Liu says. Working with Google, he says, will "change the equation."

Google says it has 100 billion searches per month.

"That's just a mind-boggling number," Liu says. "It will empower local police to access that base in the interest of public safety."

Access to Google's vast audience will help police send warnings, traffic reports, school lockdowns, missing children bulletins and other public safety alerts to more people, says Capt. Mike Parker, spokesman for the Los Angeles County Sheriff's Department.

LASD signed up for the free Nixle service — there's also a paid premium version — three years ago, Parker says. Although the department posts information on its website, Twitter and Facebook, not all residents use social media or have smartphones, he says.

About 30,000 people in a county of more than 10 million now subscribe to the department's Nixle alert system, he says.

The link to Google "is going to have a huge impact," Parker says. "We're going to get more information to more people sooner."

The new partnership expands Google's year-old alert system, which began Jan. 25, 2012, with warnings issued by the National Weather Service, the U.S. Geological Survey and the National Oceanic and Atmospheric Administration appearing on Google Maps, Google communications manager Kate Parker says. Google has since added the Japan Meteorological Agency and AMBER alerts for missing children. Nixle adds "hyper-local" police information, she says.

During Hurricane Sandy, which struck the East Coast in October, Google posted public alerts including evacuation routes, lists of shelters and other emergency information, Parker says.

"Increasingly," Parker says, "people are turning to the Internet when a disaster happens."